The invention concerns a medullary pin for a distraction and subsequent lengthening of a tubular bone with segment transport.
Medullary pins are known from the prior art, such as DE 10 2011 053 638 A1, which make possible a distraction of long tubular bones with segment transport. Two bone fragments, a distal end fragment and a proximal end fragment, are displaced relative to each other by means of a medullary pin. Furthermore, a middle bone fragment exists in applications with segment transport, also being known as the segment and likewise being part of the fractured bone. At a contact site between one of the end bone fragments and the middle fragment, bone is supposed to grow back. This is accomplished by selecting the rate of advance of the middle fragment for the distraction to be sufficiently small.
Such displacements enable a treatment of major bone defects of more than 3 cm, for example, such as may occur as a result of diseases or violent impact. Major bone defects may also occur in operations due to bone tumors, which can be treated with a medullary pin with segment displacement depending on the severity of the disease.
One challenge in the case of medullary pins with transport of a middle fragment is principally the fixation of the ends of the medullary pin in the proximal bone fragment and the distal bone fragment. Especially in the case of short fragments at the ends of the bone, the medullary pins known from the prior art can be hard to anchor.
The problem of the invention is to indicate a medullary pin, wherein systems or medullary pins known from the prior art should be improved, in particular, the drawbacks of the prior art should be mitigated or eliminated. Medullary pins are desirable which require the least possible surgical expense or which enable a dependable fixation even in short bone end fragments.